The present invention relates to an impression tray for dental prostheses, comprising a channel, to take the impression paste, curved in a U shape with diverging arms in a plane roughly parallel to the bottom of the channel, this channel being provided with paste retention means and being prolonged, on the opposite side from its two ends, by a handle to hold it with.
These impression trays are used to take an impression of the teeth in a jaw, from which impression the prosthetist mades a plaster model.
So far impression trays have been made in pressed sheet metal, with the paste being retained in the channel by means of holes perforated in it.
There are many drawbacks to these known impression trays.
Although the impression trays are made of deformable thin sheet metal difficulties arise in stripping the plaster model from the impression and in subsequently removing the impression from the impression tray. In general the impression is damaged or even destroyed. It is therefore not possible to re-use the impression.
Because the impression trays must be deformable in order to allow for stripping they are not rigid enough for application of the so-called "wash technic" method of taking the impressions in two stages, which involves using more rigid silicone-based paste.
Furthermore it is awkward to clean the impression tray since the paste adheres to the retention perforations.
There also exist impression trays, also made of pressed steel, in which paste retention is assured by means of metal wires welded to the top inside edges of the channel. Here again, it is necessary to deform the impression tray to strip the mold. In addition the paste risks being detached from the bottom of the channel, because there is no retention means at that position, when the impression is separated from the jaw (withdrawal). In addition, the fact that there are metal wires on the inside top edges of the channel makes it necessary to make the channel itself very wide, so leading to the use of a large amount of paste.